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Demonstration of ACROSS sources phased array in a deep underground site

在地下深处进行跨源相控阵演示

基本信息

批准号：
14350240
负责人：
HIGASHIHARA Hiromichi
金额：
$ 9.6万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

A hardware system of new seismic active monitoring method, ACROSS, has been developed. The core hardware is a rotational source. The source rotates an eccentric mass with a constant frequency, the rotation generates centrifugal force and the centrifugal force emits harmonic elastic waves in the ground. The emitted waves are extremely coherent and stable in time. Therefore, one is able to observe some temporal variation of the waves that propagates through a fault zone. The results of this research are as follows ;1)ACROSS system was established in our experimental site. An ACROSS source and three bore-hole type accelerometers were settled on a hard rock in a deep underground. In order to synchronize between the rotation of the source and sampling timing, the source and observation system are linked by means of optical cables. Timing signals generated by the source were transported to the AD converter in the observation system.2)Micro-tremors were observed, and the noise condition was evaluated quantitatively.3)The ACROSS source was driven several times. The emitted waves were observed by using three accelerometers that were equipped at 1 m, 300 m and 1000 m far from the source. In a row time series data, one can not detect the emitted harmonic waves. However, because of the coherency of the emitted waves and the synchronization between the source and the receivers, the emitted waves were accurately estimated. From this experiment, we found that the generated harmonic waves were fairly stable in time. The temporal stability of the waves observed at 1 m site was 0.1% in amplitude and 100 micro-seconds in phase.4)Fifteen components of frequency response were observed and sompi-cepstrum method wad applied to the observed data. An arrival time of P wave was detected.

研制了地震主动监测新方法CROSS的硬件系统。核心硬件是旋转源。震源以恒定频率旋转一个偏心质量，旋转产生离心力，离心力在地面上发出简谐弹性波。发射的波在时间上是非常相干和稳定的。因此，人们能够观察到通过断裂带传播的波的一些时间变化。本研究取得的成果如下：1)在我们的实验场地建立了跨平台系统。一个跨源式和三个孔洞式加速度计安装在地下深部的一块坚硬岩石上。为了使信号源的旋转与采样定时同步，信号源与观测系统通过光缆连接。由信号源产生的时序信号被传输到观测系统中的AD转换器。2)观测到微动，并对噪声状况进行定量评估。3)多次驱动交叉信号源。发射的波是用三个加速度计观测的，分别安装在离震源1米、300米和1000米的地方。在连续的时间序列数据中，人们无法检测到所发出的谐波。然而，由于发射波的相干性以及源和接收器之间的同步性，发射波被准确地估计出来。从实验中我们发现，产生的谐波在时间上是相当稳定的。在1m处观测到的波形的时间稳定度为0.1%，相位为100微秒。4)观测到了15个频率响应分量，并对观测数据进行了倒频谱分析。检测到P波的到达时间。